70-200mm 2.8 IS - needs different MA for different distances

I'm not sure if this is the camera or the lens.
I'm using 7D

@ 200mm f2.8 on both
when I shoot something at around 10 ft, I would need +5 MA
but when I shoot something at around 40 ft, I would need +15 MA

Would this be a lens issue, and I need to send it in... since it's still under warranty?

Have you ruled out all other variables besides the lens?

This is the major problem with MA. I wish Canon would add at least one more preset to it. So, then you can MA for short and for long.

Or of course, you can just gets primes instead.

The problem is not with the focal length, but the distance of the subject.

Todd Lambert wrote in post #8997276
This is the major problem with MA. I wish Canon would add at least one more preset to it. So, then you can MA for short and for long.

Or of course, you can just gets primes instead.

If you have someone 10ft away and you are at 70mm. Then the person is 40ft and you're still at 70mm? That type of thing?

yes, but both at 200mm.

Hmm, not sure, but object distance shouldn't matter. It either front focuses or it back focuses which you can correct with MA. If it's doing something other than those, then yes, probably need to send it in.

At 10 feet then there's a chance that aberrations may be influencing the AF performance a little. Logically, most of us would use the centre AF point for a test like this but it would be interesting to see if the results differed using one of the outer points (appreciating that overall AF accurracy might be degraded)

Bob

yes, when testing I used center focus point only.

Basically, when shooting something around 10 ft away, I would need +5 MA, but when farther away at around 30-40 ft with the same +5 MA, it would be front focusing. Which need a +15 MA to get a sharp picture.

What does +15 look like at 10ft? 10ft I think is too close to MA that lens at 200mm though in my opinion.

get it calibrated. I got my 70-200 2.8 IS repaired and it's the sharpest at 0 MA with my 7D

Yes, I certainly have this problem as well. With the 70-200/2.8IS I haven't much bothered switching up the MA (not so critical to my work, I got it set at about 25 meters and let it be), but with my 85L, it is mandatory if I want to get acceptable results at f1.2. Head-shoulders portraits is +0 but for full-body distances, +5. I learned this the hard way after my first time going outside with the lens and losing about 1/2 the shots to FF.

Todd Lambert wrote in post #8997476
Hmm, not sure, but object distance shouldn't matter. It either front focuses or it back focuses which you can correct with MA. If it's doing something other than those, then yes, probably need to send it in.

No .. from my observation and testing of my 70-200 F4 and Tamron 60mm F2 macro. The distance to object (focus distance) do matters in some of the lens. For example, it is well know that the 70-200 image is soft (or actually cannot focus) at the minimum focus distance (MFD) of 1.2m at focal length of 200mm.

When I test the Tamron 60mm F2 macro, it is even worse. It focus ok at macro distance (0.3m-1m), then it becomes front focus as I step back (~1.5m), then it becomes back focus if I am very far away (>4m) from the object.

Now, I can understand why prime is preferred by some people. I think it is just technically a lot easier to make a prime that will focus properly, there is one less variable to play with. There are now 3 variables in zoom lens that can impact the image - the aperture, the focus distance, and the focal length.

Would sending it in fix the problem?